Known reactors of this type are equipped with primary heat exchangers with heat-exchange tubes of various conformations, for example, helical tubes, straight tubes, and U-shaped tubes, all of which present various drawbacks, above all in terms of overall dimensions and of fluid-dynamic and heat-exchange effectiveness.
In particular, helical-tube heat exchangers are relatively complex and costly to produce, and the tubes, albeit presenting an excellent capacity for absorbing the thermal gradients linked to their operation, require a particularly complex supporting system that can be damaged by the fluid-induced vibrations. Furthermore, to reduce the pressure losses of the primary fluid that circulates in transverse flow on the outside of the tubes, from the top down, it is necessary to limit the velocity thereof by spacing the tubes out a lot, with consequent increase in the dimensions of the heat exchanger.